0、创建Servlet

使用MyEclipse的New向导直接生成Servlet即可。

1、访问Servlet返回JSON数据

写法如下：

    <script type="text/javascript">
        function getAjax() {
            $.ajax({
                async: false,
                type: 'post',
                url: "http://localhost:8080/SdWebservice/servlet/PurchaseDataServlet",
                data: {"corpId":"04","year":"2018","areaUnit":"10000"},
                dataType: 'json',
                success:function(data) {
                    alert(data.rtn + "\r\n" + data.msg);
                }
            });
         }
    </script>

2、跨域访问

若要访问其他项目的Servlet，需要解决Servlet跨域访问的问题，访问代码如下：

    <script type="text/javascript">
        function getAjax() {
            var snVal = document.getElementById("sn").value;
            $.ajax({
                async: false,
                type: "post",
                url: "http://www.xxx.com/projname/servlet/GeoGpsServlet",
                data: {"sn": snVal},
                //dataType: 'json',
                dataType: 'jsonp',  // Servlet跨域访问
                jsonp: 'callback',  // Servlet跨域访问
                success: function(data) {
                    console.log(data);
                    alert("id=" + data.id + "\r\nsn=" + data.sn + "\r\nlon=" + data.lon + "\r\nlat=" + data.lat);
                }
            });
         }
    </script>

后台需要对返回的JSON字符串进行简单处理

public class GeoGpsServlet extends HttpServlet {
    
    ...

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String c = request.getParameter("callback"); ////////// 看这里 //////////
        
        // 得到查询参数
        String sn = request.getParameter("sn");
        
        // 得到5分钟之前的时间
        Date now = new Date();
        long start = now.getTime() - 5 * 60 * 1000;
        Date startTime = new Date(start);
        
        StringBuilder sb = new StringBuilder();
        sb.append("from GeoGps ");
        sb.append("where sn='").append(sn).append("' ");
        sb.append("and createTime>? ");
        sb.append("order by createTime desc ");
        
        String jsonStr = "{}";
        List<GeoGps> list = geoGpsService.getListByHql(sb.toString(), startTime);
        if (null != list && !list.isEmpty()) {
            GeoGps gps = list.get(0);
            Gson gson = new Gson();
            jsonStr = gson.toJson(gps);
        }
        
        //response.setHeader("Access-Control-Allow-Origin", "*");
        response.setContentType("text/html;charset=utf-8");
        PrintWriter out = response.getWriter();
        out.println(c + "(" + jsonStr + ")"); ////////// 看这里 //////////
        out.flush();
        out.close();
    }
}

3、跨域访问htts的Servlet

服务端需要加上

        response.setHeader("Access-Control-Allow-Origin", "*");

4、Struts2拦截器

Struts2的拦截器会对Servlet进行拦截，原先的web.xml

  <filter-mapping>
    <filter-name>struts2</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

把上面的写法替换如下：

  <filter-mapping>
    <filter-name>struts2</filter-name>
    <url-pattern>*.action</url-pattern>
  </filter-mapping>
  <filter-mapping>
    <filter-name>struts2</filter-name>
    <url-pattern>*.jsp</url-pattern>
  </filter-mapping>
  <filter-mapping>
    <filter-name>struts2</filter-name>
    <url-pattern>*.html</url-pattern>
  </filter-mapping>
  <filter-mapping>
    <filter-name>struts2</filter-name>
    <url-pattern>*.htm</url-pattern>
  </filter-mapping>